Aerators for waste treatment systems must be designed to optimize multiple tradeoffs, to provide the best aeration at the lowest cost, with the least maintenance. Ideally, a small number of aerators would provide a large area of bubbles to contact as much water as possible in the waste treatment system. More aerators increases costs of the system due to the cost of the aerators themselves and the piping to supply air to them, so the least number aerators to achieve a high level of aeration is desirable.
Treatment of wastewater is more effective when air bubbles make contact with as much water in the system as possible. In order to contact as much of the water in the treatment system as possible, the aerators should be placed as near the bottom as possible so that the air can percolate upwardly through the most water possible. However, if the aerators are placed too near the bottom, sediment in the water may clog the porous diffuser stones that are typically used in aerators. Thus, the stones should be placed at a height that keeps the stones out of sediment, but still near the bottom of the tank of the treatment system.
Maximizing the bubbles' contact with water also means that the projected area of the diffusers, as viewed from above the aerators, should be as large as possible. The larger the cloud of bubbles emanating from the aerator, the more water will be in contact with bubbles from the aerator. If for instance, multiple diffuser stones are placed vertically directly above one another, the projected area of the diffusers as viewed from above will be much less than if the stones are spread apart. The larger the projected area viewed from above is, the larger the cloud of bubbles will be that percolates upward through the water.